(a). Field of the Invention
The invention relates to communication systems, and more particularly to a receiver architecture for the communication system.
(b). Description of the Prior Arts
In a communication system, the receiver and the transmitter may operate in different clock frequencies, that is, the receiver and the transmitter may belong to different clock domains. Thus, the communication system needs a synchronization mechanism to adjust the clock phase and frequency to let the receiver and the transmitter be synchronous, thereby transceiving data correctly.
In prior arts, the synchronization solution is analog-based. That is, the receiver estimates a timing error of a received signal resulted from different clock phase and frequency between the local receiver and the far-end transmitter, and then feedbacks the estimated timing error to the clock source (e.g. an oscillator) of the receiver, so as to directly adjust the phase and frequency of the clock source to be synchronous as that of the transmitter and thus achieve the synchronization. However, this analog-based solution has disadvantages. That is, the direct adjustment of the phase and frequency of the clock source will introduce more clock jitter. Considering a longer time period, the clock phase and frequency of the receiver may have small error in comparison with the transmitter, and each respective clock is likely to have jitter. This will cause signal sampling errors and consequently results in errors in data reception.
Besides, since the receiver receives data and interference simultaneously, the synchronization problem also exists when the interference cancellation is performed. For example, in a full duplex communication system, since the transmission and reception of signals are performed simultaneously in the same channel, the received signal of a receiver at one side of the channel includes both the signal transmitted by a transmitter at the other side and the echo resulted from the signal transmitted by a transmitter at the same side as the receiver. Further, in a multi-channel communication system, the received signal of a receiver at one side of a channel includes both the signal transmitted by a transmitter at the other side of the same channel and the cross talk resulted from the signal transmitted by transmitters in other channels. In order to cancel the echo or cross talk, an echo canceller or cross talk canceller is used to simulate and generate the echo or cross talk signal, and then the simulated echo or cross talk signal is used to cancel the true interference in the received signal of the receiver. However, since these cancellers perform the simulation according to the data transmitted by a certain transmitter which may belong to a clock domain different from the receiver, the simulated echo or cross talk may also belong to a clock domain different from the received signal of the receiver. Thus, it is necessary to perform synchronization before canceling the echo and cross talk.